Crossover Capacitors for Accuton Tweeters - Solen -> ClarityCap -> Jupiter -> Duelund
I've got Coincident Pure Reference Extremes with an Accuton ceramic tweeter and have moved through four different capacitors to provide my high pass filtering. The speakers only have one 4.7uF capacitor in the crossover (no resistors or other components), so it was pretty easy to hear the sound of each cap.
Started with stock Solen's, then tried Clarity Cap CMR, then Jupiter Copper Foil & Wax, and finally Duelund Tinned Copper CAST. Just installed the Duelunds on Monday and despite not being broken in, they sound absolutely amazing. Smooth, sweet, and detailed without any grain or harshness. Just really spectacular, they let me hear more details while also preventing the tweeters from being aggressive, which has been a problem I've had to work hard on ever since owning the speakers.
To comment lightly about the other caps I heard, I actually thought the stock Solens were pretty good. They had a nice sense of color... when I changed out to the clarity cap, things got a little clearer, but felt too neutral. I read that they are "ruler flat" and found that a good description. I liked the cleanness, but missed some of the tone & color from the Solens... felt like I got a good combination of those two traits when upgrading to the Jupiter Copper Foils. After about 6 months of the Jupiters I finally bought the Duelunds as a self-birthday present, and they completely lived up to my (very high) expectations. Just beautiful, organic music. Can't wait to see where they go over the next 200 hours. Only have 10 to 20 on them so far.
If you've got an accuton tweeter and can handle the stupid cost (and size), I concur with everyone else's recommendations (thanks humblehifi, jeff's place, @charles1dad, & @grannyring), they will make your speakers sound better.